Perfluorovinyl ionic compounds and their use in conductive materials

ABSTRACT

The invention relates to ionic compounds in which the negative charge is highly delocalized. The compounds comprise at least one perfluorovinyl group and at least one group chosen from —O or one of the groups —NC≡N, —C(C≡N) 2 , —NSO 2 R or —C[SO 2 R] 2  or a pentacyclic group comprising at least one N, C—C≡N, CR, CCOR or CSO 2 R group. The compounds and/or their polymers are of use in the preparation of ionically conducting materials, electrolytes and selective membranes.

This application filed under 35 USC 371, claims benefit of priority fromPCT/FR98/01664 filed Jul. 27, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject matter of the present invention is ionic perfluorovinylcompounds, the polymers obtained from these compounds and theirapplications.

2. Description of the Prior Art

Polyelectrolytes of polyanion type incorporating functional groups ofsulfonate or carboxylate type are known as ion-exchange resins(polyacrylic acid, polystyrenesulfonic acid optionally crosslinked withdivinylbenzene). These polyelectrolytes are dissociated solely in thepresence of water or of highly polar protic solvents, such aspolyalcohols, for example ethylene glycol or glycerol. The correspondingacid groups (carboxylic or sulfonic acids) do not exhibit markedcatalytic properties due to the absence of swelling of the resin and thestrong association of ion pairs. In the form of membranes, thesepolymers only have a mediocre stability under the operating conditionsof a hydrogen-air fuel cell; in particular, they are rapidly degraded byoxidizing species present on the oxygen electrode side. Likewise, thesepolymers cannot be used in membrane processes, such as thechlorine-sodium hydroxide electrochemical process.

Furthermore, perfluorinated membranes (Nafion®) carrying sulfonic groupsare known which exhibit good chemical stability under the operatingconditions of a fuel cell and for the chlorine-sodium hydroxide process.These materials are copolymers of tetrafluoroethylene (TFE) and of acomonomer carrying sulfonyl functional groups. However, theimpossibility of crosslinking these polymers requires that the densityof ionic groups be kept low, in order to prevent the resulting polymersfrom being excessively soluble or swollen by water, resulting in amediocre mechanical strength and a relatively limited conductivity.Furthermore, these membranes exhibit a high permeability to gases(oxygen and hydrogen) and to certain solvents, such as methanol, whichis harmful to the energy efficiency of fuel cells, more especially thoseof methanol-air type (“crossover”). Furthermore, although the sulfonategroups attached to perfluorinated groups are partially dissociated inaprotic solvents and although the solvating polymers are particularlyadvantageous for secondary batteries in which the reactions at theelectrodes involve lithium ions, the conductivity of the gels obtainedby swelling Nafion® membranes with aprotic solvents, alone or as amixture, and the conductivity of the mixtures of these polyelectrolyteswith polyethers based on ethylene oxide remain too low. Furthermore, thesignificant fraction of perfluorinated segments —CF₂CF₂— resulting fromthe TFE comonomer makes these compounds sensitive to reduction atpotentials close to those of the negative electrode, resulting in thepolymer being destroyed. Moreover, the chemistry of these polymers iscomplex and expensive, and the yield in the manufacture of the monomerof perfluorovinyl ether type:

CF₂═CF—O-[CF₂CF(CF₃)]_(p)—O—CF₂CF₂SO₂F, 0≦p≦5

by thermal cracking of perfluoropolyethers-acid fluoride obtained byaddition of CF₃CF═CF₂ to isomerized sultones is low and limits the useof these materials.

Polymers which comprise anions attached to the backbone of the polymerand which are optionally plasticized or gelled by a solvent of polartype are of great advantage in electrochemical systems, such as primaryor secondary batteries, supercapacitors or systems for modulating light(electrochromic windows). Such polymers are mainly derivatives ofethylene oxide, of acrylonitrile, of polyesters of alkyl or oxaalkylacrylate or methacrylate type, or of vinylidene fluoride. The productionof monomers carrying highly delocalized anionic functional groups whichcan be incorporated, either by copolymerization or by cocrosslinking oralternatively by mixing polymers, in macromolecular materials such asthose used in the electrochemical systems described above is thereforehighly advantageous. The ionic monomers described above as components ofmembranes of Nafion® type cannot be suitable for this use because thehigh fraction of perfluorinated segments necessary in order to obtainthe maximum conductivity in aprotic media (# 1M.l⁻¹) corresponds to adecreased dielectric constant in the vicinity of the ions and to anincreased segmental stiffness, which are unfavorable to the movement ofthe ions. Moreover, the sulfonate groups are insufficiently dissociatedin comparison with the salts of anions delocalized from nitrogenouscenters or from carbon, such as, for example, the anion corresponding tothe formula (R_(F)SO₂)X(SO₂R′_(F))⁻, in which X is N, C—R orC—SO₂R″_(F), R_(F), R′_(F) and R″_(F) are chosen from fluorine andfluorinated monovalent groups, or else R_(F) and R′_(F) form thecomponents of a divalent ring, and R═H or any monovalent organicradical.

W. Navarrini et al. (U.S. Pat. No. 5,103,049) disclose methods for thepreparation of R_(f)—CF═CF—SO₂F compounds in which R_(f) is F or aperfluoroalkyl group comprising 1 to 9 carbon atoms. Among thesecompounds, only CF₂═CF—SO₂F is capable of acting as basis for monomerswhich can polymerize without steric constraints. However, this materialhas been shown to be too reactive to act as a precursor for monomersalts and anions, because the nucleophilic addition to the C═C doublebond, which is depleted in electrons both by the fluorine atoms and bythe —SO₂F group, generally takes place more rapidly than thesubstitution of the fluorine of the SO₂F group, thus preventing accessto ionic monomers or to precursors of ionic compounds (“Studies of theChemistry of Perfluorovinylsulfonyl Fluoride”, Forohar Farhad, ClemsonUniversity, Thesis 1990 UMI 9115049). In particular, the methods for thepreparation of anionic compounds used with R_(F)SO₂F compounds cannot beapplied to the compound CF₂═CF—SO₂F. A process which consists inattaching a perfluorovinyl group to a phenyl nucleus carrying an SO₂Fgroup has been provided by C. Stone et al. (WO/96/39379); however, inthis case too, it is not possible to convert the CF₂═CF—C₆H₄SO₂Fmolecule to an anionic monomer because of the sensitivity of the CF₂═CF—group, which is more reactive than —SO₂F with respect to bases of OH⁻ orNH₃ type.

Another process for the preparation of monomers of the TFE typecomprising an anion has been provided by D. Desmarteau et al. (U.S. Pat.No. 5,463,005). It consists in preparing a compound comprising aperfluorovinyl group and an SO₂F group, in protecting the perfluorovinylgroup, for example by addition of Cl₂, in converting the SO₂F group toan ionic group and in then deprotecting the perfluorovinyl group. Such aprocess is nevertheless lengthy and expensive and the polymers obtainedfrom said monomers exhibit the same disadvantages as the polymers ofNafion® type, resulting from the low content of SO₃ ⁻ or sulfonimideions in the absence of crosslinking.

The aim of the present invention is to provide a novel family of ioniccompounds, which compounds exhibit extensive delocalization of thenegative charge and good activity in polymerization or incopolymerization and allow the preparation of macromolecules possessingdissociated and stable ionic functional groups, and a process for thepreparation of these compounds from fluorinated derivatives which arecommercially available at low cost, for example hydrofluorocarbons orhalocarbons.

For this reason, the subject matter of the present invention is ionicmonomer compounds, the homopolymers and the copolymers obtained fromthese compounds, their applications and a process for their preparation.

SUMMARY OF THE INVENTION

A compound according to the invention is an ionic compound in which thenegative charge is highly delocalized and which corresponds to theformula [CF₂═CF—A⁻]_(m)M^(m+), in which:

M^(m+) is a proton or a metal cation having the valency m chosen fromthe ions of alkali metals, of alkaline earth metals, of transitionmetals or of rare earth metals or an organic onium cation or anorganometallic cation, 1≦m≦3;

A⁻ represents an anionic group corresponding to one of the followingformulae:

[—(CF₂)_(n—SO) ₂Z]⁻  (I)

[—(O)_(n′)—Φ—SO₂Z]⁻  (II)

n and n′ represent 0 or 1;

Φ represents a condensed or noncondensed aromatic group, which may ormay not carry one or more substituents and which may or may not compriseheteroatoms, or a polyhalogenated group —C₆H_((4−x−y))F_(x)Cl_(y)—(1≦x+y≦4);

Z represents —O or one of the —NC≡N, —C(C≡N)₂, —NSO₂R or —C[SO₂R]₂groups, Z being other than —O when n or n′ are zero;

D represents a single bond, an oxygen atom, a sulfur atom, a —CO—carbonyl group or an —SO₂— sulfonyl group;

the groups X¹ to X⁴, hereinafter denoted by X^(i), represent N, C—C≡N,CR, CCOR or CSO₂R, it being understood that, in a pentacyclic group, thexi groups can be identical or different;

R represents Y, YO—, YS—, Y₂N—, F, R_(F)═C_(q)F_(2q+1) (preferably0≦q≦12), CF₂═CF—, CF₂═CFCF₂— or CF₂═CF—O—, it being understood that, if2 R substituents are present on the same group, they can be identical ordifferent;

Y represents H or a monovalent organic radical having from 1 to 16carbon atoms chosen from alkyl, alkenyl, oxaalkyl, oxaalkenyl, azaalkyl,azaalkenyl, aryl or alkylaryl radicals or from the radicals obtainedfrom the abovementioned radicals by substitution, in the chains and/orthe aromatic part, by heteroatoms, such as halogens, oxygen, nitrogen,sulfur or phosphorus, it being understood that if sulfur or phosphorusare present, they can optionally be bonded to substituted nitrogen oroxygen atoms, or else Y is a repeat unit of a polymeric backbone.

The divalent radical Φ can be a phenyl C₆H₄ corresponding to the ortho,meta and para positions of substitution. It can be an aromatic group, aphenyl which is substituted and/or comprising condensed nuclei which mayor may not comprise heteroatoms. Φ is preferably a halogenated phenylgroup or a phenyl group carrying 1 to 2 CF₃ substituents or a pyridylnucleus.

When M^(m+) is a metal cation, it can be an alkali metal (in particularK⁺ or Li⁺), an alkaline earth metal (in particular Mg⁺⁺, Ca⁺⁺ or Ba⁺⁺),a transition metal (in particular Cu⁺⁺, Zn⁺⁺ or Fe⁺⁺) or a rare earthmetal (in particular Re⁺⁺⁺).

When M^(m+) is an onium cation, it can be chosen from ammonium ions[N(Y^(j))₄]⁺, amidinium ions RC[N(Y^(j))₂]⁺, guanidinium ionsC[N(Y^(j))₂]₃ ⁺, pyridinium ions [C₅N(Y^(j))₆]⁺, imidazolium ionsC₃N₂(Y^(j))₅ ⁺, imidazolinium ions C₃N₂(Y^(j))₇ ⁺, triazolium ionsC₂N₃(Y^(j))₄ ⁺, carbonium ions C₅(Y^(j))₅C⁺, NO⁺ (nitrosyl) or NO₂ ⁺ions, sulfonium ions [S(Y^(j))₃]⁺, phosphonium ions [P(Y^(j))₄]⁺ andiodonium ions [I(Y^(j))₂]⁺. In the various abovementioned onium ions,the Y^(j) substituents of the same cation can be identical or different.They represent one of the substituents indicated above for Y.

When M^(m+) is an organometallic cation, it can be chosen frommetalloceniums. It can also be chosen from metal cations coordinated byatoms, such as O, S, Se, N, P or As, carried by organic molecules, thesecations optionally forming part of a polymeric backbone. M^(m+) can alsobe a cation derived from the alkyl groups defined for Y above andlimited to those having from 1 to 10 carbon atoms, for example atrialkylsilyl, trialkylgermany or dialkylstannyl derivative; in thiscase, M is connected to [CF₂═CF—A] by a very labile covalent bond andthe compound behaves as a salt. The M^(m+) cation can also be the repeatunit of a conjugated polymer in cationic oxidized form.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Mention may be made, among the compounds of the present invention, ofthe following monofunctional monomers:

{[CF₂═CF—SO₂NCN]⁻}_(m)M^(m+), {[CF₂═CF—SO₂C(CN)₂]⁻}_(m)M^(m+),{[CF₂═CFCF₂—SO₂NCN]⁻}_(m)M^(m+), {[CF₂═CFCF₂—SO₂C(CN)₂]⁻}_(m)M^(m+),{[CF₂═CF—ΦSO₂NCN]⁻}_(m)M^(m+), {[CF₂═CF—ΦSO₂C(CN)₂]⁻}_(m)M^(m+),{[CF₂═CF—ΦSO₂NSO₂CF₃]⁻}_(m)M^(m+), {[CF₂═CF—ΦSO₂C(SO₂CF₃)₂]⁻}_(m)M^(m+),{[CF₂═CF—ΦSO₂CH(SO₂CF₃)]⁻}_(m)M^(m+),

Mention may also be made of the following di- and trifunctional monomers{[(CF₂═CFCF₂—SO₂)₂N]⁻}_(m)M^(m+), {[(CF₂═CFSO₂)₂CH]⁻}_(m)M^(m+),{[(CF₂═CFCF₂—SO₂)₂CH]⁻}_(m)M^(m+), {[(CF₂═CF—SO₂)₃C]⁻}_(m)M^(m+),{[(CF₂═CFCF₂—SO₂)₃C]⁻}_(m)M^(m+), {[(CF₂═CF—ΦSO₂)₂N]⁻}_(m)M^(m+),{[(CF₂═CF—O—ΦSO₂)₂N]⁻}_(m)M^(m+), {[(CF₂═CF—ΦSO₂)₂CH]⁻}_(m)M^(m+),{[(CF₂═CF—O—ΦSO₂)₂CH]⁻}_(m)M^(m+), {[(CF₂═CF—ΦSO₂)₃C]⁻}_(m)M^(m+),{[(CF₂═CF—O—ΦSO₂)₂CH]⁻}_(m)M^(m+), {[(CF₂═CF—ΦSO₂)₃C]⁻}_(m)M^(m+),{[(CF₂═CF—O—ΦSO₂)₃C]⁻}_(m)M^(m+), {[(CF₂═CF—)₂C₆H₃SO₃]⁻}_(m)M^(m+),{[3,5-(CF₂═CF—)₂C₆H₃SO₂NSO₂CF₃]⁻}M^(m+)

Preference is very particularly given, among the abovementionedcompounds, to those in which Φ is —C₆H₄—.

The ionic monomer compounds of the present invention can be prepared byvarious synthetic routes.

In a first embodiment, a compound comprising the perfluorovinyl group isreacted with an ionic compound having an anionic part A¹, the structureof which is analogous to that of the anionic part A of the desiredcompound, and having from one to 3 leaving groups.

The subject matter of the invention is a process for the preparation ofan ionic monomer compound [CF₂═CF—A⁻]_(m)M^(m+) as defined above inwhich an organometallic compound (OM1) is reacted in stoichiometricproportions with an ionic compound (IC1) in the presence of a catalyst,characterized in that:

the organometallic compound (OM1) corresponds to the formula(CF₂═CF—(CF₂)_(n)·_(e)—E, in which:

E represents Li, MgL¹, ZnL¹, CdL¹, Cu, Mg, Zn, Cd, Hg or atrialkylsilyl, trialkylgermanyl or trialkylstannyl group;

n is 0 or 1;

represents the valency of E;

L¹ represents a leaving group chosen from halogens, pseudohalogens,including sulfonates, radicals comprising imidazole or 1,2,4-triazolerings and their homologs in which one or more carbon atoms carrysubstituents, including those in which the substituents form a ring (forexample a benzotriazole), perfluoroalkylsulfonyloxy radicals andarylsulfonyloxy radicals;

the ionic compound (IC1) corresponds to the formula [(LA¹)⁻]_(m′)M′^(m+)in which:

M′^(m′+) represents a proton or a metal cation having the valency mchosen from ions of alkali metals, of alkaline earth metals, oftransition metals or of rare earth metals, or an organic onium cation,or an organometallic cation, 1≦m≦3. M′ is chosen so as not to interferewith the formation reaction;

L has the same meaning as L¹, it being understood that the L and L¹groups of the respective reactants used during a reaction can beidentical or different;

A¹ represents an anionic group corresponding to one of the followingformulae:

[—(CF₂)_(n)—SO₂Z¹]⁻

[—(O)_(n′)—ΦSO₂Z¹]⁻

in which:

n and n′ represent 0 or 1;

D represents a single bond, an oxygen atom, a sulfur atom, a —CO—carbonyl group or an —SO₂— sulfonyl group;

Z¹ represents the —O oxygen (except if n or n′ are zero) or one of the—NC≡N, —C(C≡N)₂, —NSO₂R¹ and —C[SO₂R¹]₂ groups;

the X′¹ to X′⁴ groups, hereinafter denoted by X′^(i), represent N,C—C≡N, CR¹, CCOR¹ or CSO₂R¹, it being understood that, in a pentacyclicgroup, the X′^(i) groups can be identical or different;

R¹ represents Y, YO—, YS—, Y₂N—, F, CF₂═CF—, CF₂═CFCF₂—, CF₂═CF—O— orR_(F)═C_(q)F_(2q+1) (0≦q≦12), or a leaving group chosen from halogens,pseudohalogens, including sulfonates, radicals comprising imidazole or1,2,4-triazole rings and their homologs, perfluoroalkylsulfonyloxyradicals and arylsulfonyloxy radicals, it being understood that, if twoR¹ substituents are present on the same group, they can be identical ordifferent and that at most two R¹ substituents are leaving groups;

Y has the meaning given above.

When the M′ cation of the reactant used is different from the M cationof the desired final compound, the compound obtained is modified byconventional cation-exchange techniques.

The preferred leaving groups L and L¹ are F, Cl, Br, I, the imidazoleradical, the trifluoromethanesulfonyloxy radical CF₃SO₃— andarylsulfonyloxy radicals.

Preference is very particularly given, for the ionic compounds (IC1), tothe following anionic groups: [(FSO₂)NSO₂R_(F)]⁻, [(ClSO₂)NSO₂R_(F)]⁻,[(ImSO₂)NSO₂R_(F)]⁻, [(FSO₂)₂N]⁻, [(ClSO₂)₂N]⁻, [(ImSO₂)₂N]⁻,[(FSO₂)NCN]⁻, [(ClSO₂)NCN]⁻, [(ImSO₂)NCN]⁻,[(FSO₂)C(R)SO₂R_(F)]⁻[(ClSO₂)C(R)SO₂R_(F)]⁻, [(ImSO₂)C(R)SO₂R_(F)]⁻,[(FSO₂)₂CR]⁻, [(ClSO₂)₂CR⁻, [(ImSO₂)₂CR]⁻, [(FSO₂)C(CN)₂]⁻,[(ClSO₂)C(CN)₂]⁻, [(ImSO₂)C(CN)₂]⁻, (FSO₂)₃C]⁻, [(ClSO₂)₃C]⁻,[(ImSO₂)₃C]⁻, [(ClΦSO₂)NSO₂R_(F)]⁻, [(BrΦSO₂)NSO₂R_(F)]⁻,[(IΦSO₂)NSO₂R_(F)]⁻, [(CF₃SO₃ΦSO₂)NSO₂R_(F)]⁻,[(CH₃ΦSO₃ΦSO₂)NSO₂R_(F)]⁻, [3,5-Br₂C₆H₃SO₃]⁻, [3,5-Br₂C₆H₃SO₂R)]⁻,[(3,5-I₂C₆H₃SO₃]⁻, [3,5-I₂C₆H₃SO₂N(SO₂R_(F))]⁻, [(BrΦSO₂)NCN⁻,[(IΦSO₂)NCN]⁻, [(CF₃SO₃ΦSO₂)NCN]⁻, (CH₃ΦSO₃ΦSO₂)NCN]⁻,[(CH₃ΦSO₂)C(CN)₂]⁻, [(BrΦSO₂)C(CN)₂], [(IΦSO₂)C(CN)₂]⁻,[(CF₃SO₃ΦSO₂)C(CN)₂]⁻, [(CH₃ΦSO₃ΦSO₂)(CN)₂]⁻, [(ClΦSO₂)N(SO₂ΦCl)]⁻,[(BrΦSO₂)N(SO₂ΦBr)]⁻, [(IΦSO₂)N(SO₂Φ)]⁻, [(CF₃SO₃ΦSO₂)N(SO₂ΦSO₃CF₃)]⁻,[(CH₃ΦSO₃ΦSO₂)N(SO₂ΦSO₃ΦCH₃)]⁻[(ClΦSO₂)₂C(SO₂R_(F))]⁻,[(BrΦSO₂)₂C(SO₂R_(F))]⁻, [(IΦSO₂)₂C(SO₂R_(F))]⁻,[(CF₃SO₃ΦSO₂)₂C(SO₂R_(F))]⁻, [(ClΦSO₂)C(SO₂R_(F))₂]⁻,[(BrΦSO₂)C(SO₂R_(F))₂]⁻, [(IΦSO₂)C(SO₂R_(F))₂]⁻,[(CF₃SO₃ΦSO₂)C(SO₂R_(F))₂]⁻, [(CH₃ΦSO₃ΦSO₂)C(SO₂R_(F2)]⁻,[BrΦC(SO₂R_(F2))⁻, [3,5-Br₂C₆H₃C(SO₂R_(F))₂]⁻,

In the abovementioned anionic groups of the compounds (IC1), R and R_(F)have the meaning given above and preferably comprise from 0 to 10 carbonatoms.

A compound (OM1) such as CF₂═CF—Li is prepared by reaction of a strongbase B and of a lithiating agent R′—Li with 1,1,1,2-tetrafluoroethane atlow temperature, according to the reaction scheme:

CF₂—CH₂F+B→CF₂═CHF+[BHF]

CF₂═CHF+R′Li→CF₂═CFLi+LiF+R′H

The compounds CF₂═CF—E in which E is other than Li can be obtained byion exchange.

It is advantageous to use butyllithium both as strong base and aslithiating agent.

The compound CF₂═CFCF₂—E can be prepared from perfluoroallylfluorosulfate by simple nucleophilic substitution according to thefollowing reaction scheme:

CF₂═CFCF₂—SO₃F+M⁺E⁻→CF₂═CFCF₂—E+M⁺SO₃F⁻

KI is a particularly appropriate compound M⁺E⁻.

The organometallic compounds (OM1) are more particularly chosen from:CF₂═CFLi, (CF₂═CF)_(2−x)Mg(Hal)_(x), (CF₂═CF)_(2−x)Zn(Hal)_(x),(CF₂═CR)_(2−x)Cd(Hal)_(x) (0≦x≦2); Hal═Cl, Br, I, pseudohalogen),(CF₂═CF)_(3−y)Al(Hal)_(y), (0≦y<3); CF₂═CFCu, CF₂═CFSi(CH₃)₃,CF₂═CFSi(C₂H₅)₃, CF₂═CFSn(CH₃)₃, CF₂═CFSn(C₂H₅)₃, CF₂═CFSn(C₄H₉)₃,CF₂═CFCF₂CdBr, CF₂═CFCF₂Cu, CF₂═CFCF₂Zn(O₃SF), CF₂═CFCF₂Si(CH₃)₃ andCF₂═CFCF₂Si(C₂H₅)₃.

It is known to a person skilled in the art that the stability and theprocessing conditions for halogenated organometallic compounds varyaccording to the nature of E; in particular, organolithium compounds areonly stable at temperatures of less than −60° C. and are habituallyprepared and used at the temperature of dry ice, whereas more covalentcompounds, such as silane derivatives, are stable even above roomtemperature.

The process is carried out in the presence of a catalyst chosen fromderivatives of nickel or palladium coordinated with bases of amine orphosphine type. Mention may be made, by way of example, of nickelbis(2,2′-bipyridyl), nickel tetrakis(triphenylphosphine) and itssulfonated derivatives, palladium acetate,trisbenzylideneketonedipalladium, palladium tetrakis(triphenylphosphine)and its sulfonated derivatives, and the compounds obtained byreplacement of two triphenylphosphine molecules by [(C₆H₅)₂PCH₂]₂ or[(C₆H₅)₂PCH₂]₂CH₂. Nickel and palladium have catalytic properties forso-called Suzuki coupling reactions when their degree of oxidation isgreater than or equal to 0 and less than or equal to 2.

In another embodiment of the invention, an ionic monomer compound[CF₂═CF—A⁻]_(m)M^(m+) according to the invention is prepared by reactinga compound comprising a protected fluorovinyl groupCF₂L³CFL⁴—(CF₂)_(n)E¹ with a reactant [(L⁵)_(a)A²]_(m′)M′^(m′+) makingpossible the formation of the anionic group A and then the protectivegroups are removed by a chemical or electrochemical reduction or by adehydrohalogenation. M′ has the meaning indicated above. L³ and L⁴represent H or a halogen, just one among them optionally being H. E¹ hasthe meaning given above for E. L⁵ represents a leaving group having thesame definition as the leaving group L. “a” is the valency of theanionic group A². A² represents a group corresponding to one of thefollowing formulae [—(CF₂)_(n)—SO₂Z²]⁻, [—(O)_(n′)—ΦSO₂Z²]⁻ or

in which:

n, n′, D and Φ have the meaning indicated above;

Z² represents the —O oxygen (except if n or n′ are zero) or one of thegroups —NC≡N, —C(C≡EN)₂, —NSO₂R² or —C[SO₂R²]₂; the groups X″¹ to X″⁴,hereinafter denoted by X″^(i), represent N, C—C≡N, CR², CCOR² or CSO₂R²,it being understood that, in a pentacyclic group, the X″^(i) groups canbe identical or different;

R² represents OH, —SH, Y, YO—, YS—, Y₂N—, F, CF₂═CF—, CF₂═CFCF₂—CF═CF—O—or R_(F)═C_(q)F_(2q+1) (0≦q≦12), it being understood that, if two R²substituents are present on the same group, they can be identical ordifferent and that at most two R substituents represent —OH or —SH;

Y has the meaning given above.

Mention may be made, by way of example, of the following reaction:

(ClSO₂)₂NK+2CF₂Cl—CFClLi→(CF₂Cl—CFClSO₂)₂NK+2LiCl.

When the cation M′ of the reactant used is different from the cation Mof the desired final compound, the compound obtained is modified byconventional cation-exchange techniques. The greater resistance of thecompounds thus protected with respect to nucleophiles, in particularbases, makes it possible to carry out reactions on molecules acting asintermediate in the preparation of the monomer anions, reactions whichwould be impossible if the ethylenic double bond was unprotected. Inparticular, it is possible to form intermediates of sulfamide orhydrazide type allowing the construction of anionic species.

For example, the anion derived by addition of chlorine totrifluoroacrylic acid can be converted to a triazole group via ahydrazide. The triazole anion, more dissociated than the carboxyl anion,is obtained according to the simplified scheme:

The starting fluorinated acrylic acid is easily prepared by reaction ofCO₂ with an organometallic derivative, such as CF₂═CFLi, itself easilyobtained by reaction of an alkyllithium with the commercial compound1,1,1,2-tetrafluoroethane sold under the tradename Klea®.

Similar reactions are possible with a compound comprising a sulfur-basedanionic group, such as a sulfonate. They make it possible to obtain, viaa sulfamide, a compound comprising an anionic sulfonylimide group whichis more dissociated than the sulfonate group, by the following reactionstages:

sulfonate+chlorinating agent→RSO₂Cl

RSO₂Cl+NH₃→RSO₂NH₂;

RSO₂NH₂+R′SO₂Cl→RSO₂N(H)SO₂R′

These reactions cannot be carried out if R═CF₂═CF. On the other hand,the desired result is obtained if R═CF₂Cl—CFCl and, for example, R′═R orCF₃. The sulfonate is easily obtained by the following reactions:

CF₂Cl—CFClLi+ClSO₃Si(CH₃)₃→CF₂Cl—CFSO₃Li+ClSi(CH₃)₃.

A compound [CF₂L²—CFL³—(CF₂)_(n)]—E¹, in particular CF₂ClCFClLi, can beobtained by reaction of the corresponding compound [CF₂═CF—(CF₂)_(n)]—E¹with a compound L²L³ at a temperature of between −80° C. and 110° C.,for example in the Trapp mixture (THF/ether pentane composition).Mention may be made, among the compounds L²L³ which are easily added tothe perfluorovinyl double bond, of FCl, Cl₂, ClBr, Br₂, ICl, IBr, I₂,(SCN)₂, HCl, HBr and HI. The lithium compounds (OM2) can act as thebasis for the preparation of other organometallic compounds, such assilicon or zinc derivatives, by exchange.

The (L²)/(L³) and L²H pairs are preferably chosen from Cl₂, Br₂, FCl,FBr, BrCl, ICl, HF, HCl and HBr, Cl₂ and HCl being particularlypreferred.

The L²L³ groups are easily removed by reduction or bydehydrohalogenation. The reducing agent is advantageously chosen fromzinc, the copper-zinc couple, Ti³⁺, V²⁺, Cr³⁺ or Sm²⁺ salts, andtetrakis(dimethylaminoethylene) {[(CH₃)₂N]₂C═}₂. An electrochemicalreduction can also be carried out, directly or via the preceding metalsacting as mediators. The dehydrohalogenating agents are chosen fromstrong bases and are known to a person skilled in the art. Mention mayin particular be made of NaH [optionally used in the presence ofphosphorus-comprising bases of phosphazene P1-P4 type (Fluka AG, Basle,Catalog No. 79408, 79412, 79417, 79421, 422 79432)], (CH₃)₃CONa,(CH₃)₃COK, LDA (lithium diisopropylamide), [(CH₃)₂CH]₂NLi, orhexaalkyldisilazane derivatives, in particular [(CH₃)₃Si]₂NLi,[(CH₃)₃Si]₂NNa and (CH₃)₃Si]₂NK.

In another embodiment, an ionic compound having an anionic part A³, thestructure of which is analogous to that of the anionic part A of thedesired compound, and having from one to 3 hydroxyl or thiol groups isreacted with a compound comprising the perfluorovinyl group.

The subject matter of the invention is a process for the preparation ofan ionic monomer compound [CF₂═CF—A⁻]_(m)M^(m+) as defined above,characterized in that a compound CF₂═CFL², in which L² represents Cl, Bror F, is reacted in stoichiometric proportions with an ionic compound(IC2) [(HQA³)⁻]_(m′)(M′)^(m+) and in that the addition product obtainedis treated with a strong base B.

The reaction scheme is as follows:

CF₂═CFL²+(HQA³)⁻→HCF₂—CFL²—Q—A³

HCF₂—CFL²—Q—A³+Base →CF₂═CF—Q—A³+BaseHI

The cationic part (M′)^(m′+) has the meaning given above, alkali metalcations being preferred.

The anionic part (HQA³)⁻ is such that:

Q represents O or S;

A³ represents an anionic group corresponding to one of the followingformulae:

in which:

n and Φ have the meaning indicated above;

Z³ represents the —O oxygen (except if n is zero) or one of the groups—NC≡N, —C(C≡N)₂, —NSO₂R³ or —C[SO₂R³]₂;

the groups X″′¹ to X″′⁴, hereinafter denoted by X″′^(i), represent N,C—C≡N, CR³, CCOR³ or CSO₂R³, it being understood that, in a pentacyclicgroup, the X″′^(i) groups can be identical or different;

R³ represents HO—, HS—, Y, YO—, YS—, Y₂N—, F, CF₂═CF—, CF₂═CFCF₂—,CF₂═CF—O— or R_(F)═C_(q)F_(2q+1) (0≦q≦12), it being understood that, iftwo R³ substituents are present on the same group, they can be identicalor different and that at most two R³ substituents are —OH or —SH groups;

Y is as defined above.

The strong base B can be in particular NaH [optionally used in thepresence of phosphorus-comprising bases of phosphazene P1-P4 type (FlukaA G, Basle, Catalog No. 79408, 79412, 79417, 79421, 422 79432)],(CH₃)₃CONa, (CH₃)₃COK, LDA (lithium diisopropylamide), [(CH₃)₂CH]₂NLi,or hexaalkyldisilazane derivatives, in particular [(CH₃)₃Si]₂NLi,[(CH₃)₃Si]₂NNa and [(CH₃)₃Si]₂NK. Potassium t-butoxide is particularlyappropriate.

When the ionic compound (IC2) comprises a thiol, it is possible toconvert the sulfide of the anion [HCF₂—CFL²SA]⁻ of the intermediateproduct obtained to the sulfone by oxidation. The electro-withdrawingpower of the sulfone contributes to decreasing the basicity of thecorresponding anion [HCF₂—CFL²—SO₂—A]⁻ and it is then possible to removeL²H under mild conditions, for example in the presence of a tertiarynitrogenous base. The preferred compounds (IC2) are those which compriseone of the following anions:

[{HO—(Φ)SO₂}N(SO₂R_(F))]⁻, [{HS—(Φ)SO₂}N(SO₂R_(F))]⁻, [{HO(Φ)SO₂}NCN]⁻,[{HS(Φ)SO₂}NCN]⁻, [{HO(Φ)SO₂}C(CN)₂]⁻, [{HS(Φ)SO₂}C(CN)₂]⁻,[{HO(Φ)SO₂}N{SO₂(Φ)OH}]⁻, [{HS(Φ)SO₂}N(Φ)SH]⁻, [{HO(Φ)SO₂}₂C(R)]⁻,[{HO(Φ)SO₂}₂C(SO₂R)]⁻, [{HO(Φ)SO₂}₂C(SO₂R_(F))]⁻,[{HO(Φ)SO₂}C(SO₂R_(F))₂]⁻, [{HS(Φ)SO₂}₂C(R)]⁻, [{HS(Φ)SO₂}₂C(SO₂R)]⁻,[{HS(Φ)SO₂}₂C(SO₂R_(F))]⁻, [{HS(Φ)SO₂}C(SO₂R_(F))₂]⁻,[3,5-(HO)₂—C₆H₃C(SO₂R_(F))]⁻, [(3,5-(HO)₂—C₆H₃SO₂)N(SO₂R_(F))]⁻,[3,5-(HO)₂—C₆H₃C(SO₂R_(F))]⁻, [{HO—(Φ)SO₂}₂C(SO₂R_(F))]⁻,[{HS—(Φ)SO₂}₂C(SO₂R_(F))]⁻,

In another embodiment, the compounds [CF₂═CF—A⁻]_(m)M^(m+) are preparedby a process, characterized in that it consists in reacting a compoundL⁶CF₂CF₂L⁶ with an ionic compound [(HQA³)^(−]) _(m′)(M′)^(m′+) instoichiometric proportions and in reducing the substitution compoundobtained, either chemically or electrochemically. The compound[(HQA³)⁻]_(m′)(M′)^(m+) is as defined above. L⁶ represents a leavinggroup chosen from halogens, pseudohalogens and sulfonates. Halogens areparticularly preferred.

The substitution compounds obtained are subjected to a chemicalreduction or an electrochemical reduction in order to remove the L⁶leaving groups. The reduction can be catalyzed by zinc, the copper-zinccouple, Ti³⁺, V²⁺, Cr³⁺ or Sm²⁺ salts, andtetrakis(dimethylaminoethylene) {[(CH₃)₂N]₂C═}₂. An electrochemicalreduction can be carried out, directly or via the preceding metalsacting as mediators.

The ionic compounds of the present invention, all of which comprise atleast one CF₂═CF— group, can be polymerized by the radical route. Thepolymerization can be carried out in solution or in emulsion withconventional radical initiators, such as peroxides, azo compounds,persulfates, photoinitiators of benzoin type or others. During thepreparation of crosslinked materials, the molecular mass between networknodes is not necessarily very high, which constitutes a significantadvantage with respect to materials of the Nafion type.

A polymer according to the present invention is composed of apolyanionic part with which are associated cations in a numbersufficient to ensure the electronic neutrality of the polymer, thepolyanionic part being composed of repeat units:

in which A has the meaning given above in the definition of the monomercompounds of the present invention.

A polymer of the invention can also be composed of repeat units

Such a polymer is obtained by polymerization of a difunctional compoundaccording to the invention in which the anionic group A itself comprisesa perfluorovinyl radical.

Such a compound [(CF₂═CF)₂—A′⁻]_(m)M^(m+) in which M has the meaninggiven above and A′ represents an anion corresponding to one of theformulae (I), (II) or (III) mentioned above in which a Z or X^(i)substituent comprises a perfluorovinyl radical. In this case, twoperfluorovinyl radicals form a ring comprising 4 carbons which isconnected to an analogous ring via the anionic part A′ in order to forma linear polymer.

The polymerization can be carried out starting from only the compoundsof the invention and a homopolymer is obtained in which each of therepeat units carries an ionic group.

When the polymerization is carried out in the presence of a comonomer,it is possible to limit the amount of ionic groups on the copolymer.

The polymerization of monofunctional monomers makes it possible toobtain linear polymers. The polymerization of di- or trifunctionalmonomers, in which the anionic group A itself comprises one or twoadditional CF₂═CF— groups, makes it possible to obtain crosslinkedmacromolecular materials. In this case also, a copolymerization with acomonomer not carrying ionic groups makes it possible to adjust thenumber of functional groups introduced.

Generally, when the compounds of the present invention are polymerizedin the presence of a comonomer, the choice of the monomer, of thecomonomer and of the number of polymerizable groups on the monomer andthe comonomer makes it possible to adjust the properties of themacromolecular materials obtained according to the use which isanticipated for them.

The ionic compounds of the present invention comprise at least oneionophoric group. They can thus be used for the preparation of ionconducting materials. The polymers obtained from the monomer compoundsof the invention, which have the property of polymerizing or ofcopolymerizing, comprise repeat units carrying an ionophoric group andcan thus also be used for the preparation of ion conducting materials,with the advantage of having an immobile anionic charge. An ionconducting material constituted by an ionic monomer compound in solutionin a solvent and an ion conducting material comprising a polymerobtained by polymerization of a monomer compound of the presentinvention consequently constitute further subject matters of the presentinvention.

The ion conducting materials of the present invention can be used forthe preparation of the electrolyte or as binder of the electrodes ofenergy storage systems, such as primary or secondary batteries, fuelcells, in supercapacitors, in systems for modulating light transmission(electrochromic systems, electroluminescent diodes) or in sensors. Anelectrolyte obtained from a compound according to the invention can be aliquid electrolyte, a solid electrolyte or a gel electrolyte.

A plasticized electrolyte or an electrolyte in the gel form according tothe invention can be composed of a mixture of at least one polarsolvent, of an ionic monomer compound of the invention and of a polarpolymer. It can also be composed of at least one polar solvent and apolymer or copolymer obtained by polymerization of a monofunctionalcompound according to the present invention.

A solid electrolyte according to the invention comprises either acopolymer of at least one compound according to the invention and of oneor more precursors of solvating polyethers or a macromolecular materialobtained by co-crosslinking of at least one compound according to theinvention and of a solvating polyether carrying reactive functionalgroups capable of reacting with the perfluorovinyl group of thecompounds of the invention. In another embodiment, a solid electrolytecan comprise a mixture of a polyether and of a homopolymer or of acopolymer obtained from at least one compound of the invention carryingionic groups, it being possible for said mixture optionally to becrosslinked in order to form an interpenetrating network. In some cases,it can be advantageous to plasticize the macromolecular material byaddition of a polar solvent which is compatible with the etherfunctional groups. Depending on the amount of polar solvent added, theelectrolyte will be a plasticized solid electrolyte or a gelelectrolyte. The polar solvent is chosen, for example, from linearethers and cyclic ethers, esters, nitrites, nitro derivatives, amides,sulfones, alkylsulfamides and partially halogenated hydrocarbons.

An electrolyte can also be composed of a mixture of a homopolymer or ofa copolymer of polar monomers (including a polyether) and of ahomopolymer or of a copolymer of ionic compounds of the presentinvention. The two mixed polymers can optionally be crosslinked to forman interpenetrating network and be plasticized by a polar liquid.

An electrolyte generally comprises a solvent (liquid, solid or gel) andat least one salt. When, in accordance with the present invention, anelectrolyte comprises a macromolecular material obtained from thecompounds of the invention, the repeat units comprise ionic groups whichcan completely or partially replace the salt conventionally added to apolymer solvent in order to constitute a polymer electrolyte. Polymersderived from trifluorovinylsulfonyl(trifluoromethylsulfonyl)imide andthose derived fromtrifluorovinylphenylsulfonyl(trifluoromethylsulfonyl)imide areparticularly advantageous for the preparation of electrolytes. Anelectrolyte obtained from a polymer according to the invention, in whichthe anions are at least partly immobilized on a polymer chain, has amainly cationic mobility, the effect of which is to greatly improve theoperation of electrochemical systems. In addition, a compound of theinvention can be used as salt added to a liquid or polymer electrolyte.

Use is preferably made, for the preparation of macromolecular materialsof use as electrolyte, of compounds according to the invention in whichthe cation is an alkali metal cation. Lithium and potassium areparticularly preferred. The more suitable anions are the mono- ordifunctional imides CF₂═CFSO₂NSO₂CF₃ ⁻ or [CF₂═CFSO₂]₂N⁻ orCF₂═CFC₆H₄SO₂NSO₂CF₃ ⁻.

When an electrolyte according to the present invention is used in anenergy storage system, such as a primary battery or a secondary battery,it is advantageous to use, as negative electrode, an electrode composedof metallic lithium or one of its alloys, optionally in the form of ananometric dispersion in lithium oxide, or double nitrides of lithiumand of a transition metal, or oxides of low potential having the generalformula Li_(4−x+y)Ti_(5+x)O₁₂ (0≦x≦1, 0≦y≦3), or carbon and carbonaceousproducts resulting from the pyrolysis of organic materials. The positiveelectrode will advantageously be chosen from vanadium oxides VO_(x)(2≦x≦2.5), LiV₃O₈ or Li_(y)N_(1−x)CO_(x)O₂ (0≦x≦1; 0≦y≦1), manganesespinels Li_(y)Mn_(1−x)M_(x)O₂ (M═Cr, Al, V, Ni, 0≦x≦0.5; 0≦y≦2), organicpolydisulfides, FeS, FeS₂, iron sulfate Fe₂(SO₄)₃, iron and lithiumphosphates and iron and lithium phosphosilicates with an olivinestructure or analogous phosphosilicates in which the iron is replaced bymanganese, and sulfophosphates with a Nasicon structureLi_(x)Fe₂S_(1−x)P_(x)O₄. The abovementioned compounds may be used aloneor as a mixture.

When an electrolyte according to the present invention is used in asystem for modulating light, such as an electrochromic system, use ispreferably made of an electrode material chosen from WO₃, MoO₃, iridiumhydroxide oxides IrO_(x)H_(y), 2≦x≦3; 0≦y≦3), Prussian blue, viologencompounds and their polymers, and aromatic polyimides.

When an ionically conducting material of the present invention is usedas electrolyte in an energy storage system, such as a supercapacitor,use is preferably made of an electrode material comprising a carbon witha high specific surface or an electrode comprising a redox polymer.

The monomer compounds of the present invention can be used for thedoping of polymers for the purpose of conferring an improved electronicconduction on them. The polymers concerned are essentiallypolyacetylenes, polyphenylenes, polypyrroles, polythiophenes,polyanilines, polyquinolines, which may or may not be substituted, andpolymers in which the aromatic units are separated by the vinylene unit—CH═CH—. The doping process consists in partially oxidizing the polymerin order to create carbocations, the charge of which is compensated forby the anions of the compounds of the invention. This doping can becarried out chemically or electrochemically, optionally simultaneouslywith the formation of the polymer. For this specific application, thechoice is preferably made of the compounds of the invention carrying ahighly delocalized charge, in particular compounds in which Z is—C(C≡N)₂, —NSO₂R or —C(SO₂R)₂, which confer thermal and mechanicalstability properties.

The compounds of the present invention can also be used to conferantistatic properties or microwave-absorbing properties on variousmaterials. The materials concerned are, for example, polymers which takepart in the composition of electronic components, textiles and windows.Homo- or copolymers of the compounds of the invention, which arepreferably non-crosslinked in order to be able to be coated onto thesurface on which the antistatic properties have to be induced, arecompounds suited to this specific use. The comonomer of this type ofapplication makes possible, if appropriate, a good adhesion to thesubstrate to be treated, by the choice of comparable polarities. Inplastics, it is also possible to prepare mixtures with the polymer ofthe invention by techniques known in plastics technology.

A copolymer obtained by copolymerization of a mixture of monofunctionalcompounds and of difunctional compounds according to the presentinvention is of use in the preparation of membranes. Thehomopolymerization or the copolymerization of the monomers according tothe invention having a perfluorovinyl functional group results in linearpolymers. It is easy, by addition of monomers having more than onepolymerizable functional group, to obtain crosslinked networks. Thesematerials can be used for preparing membranes having an improvedmechanical strength in which the degrees of swelling and the permeationin liquids in which they will be employed can be controlled. Theimprovement in the mechanical strength is also a significant factor inthe preparation of very fine membranes in which the resistance isdecreased and in the reduction of the cost of the starting materials.Likewise, controlling the degree of crosslinking makes it possible toincrease the concentration of attached ions in the membrane withoutinducing excessive solubility or excessive swelling. In processesemploying membranes, it is particularly advantageous to prepare themembrane in its definitive form, in the sheet or pipe form, from aconcentrated solution of monomers in a solvent allowing spreading orextrusion techniques, by copolymerization of the monomers, includingthose which make possible the crosslinking.

In the preparation of membranes, it is particularly advantageous to usemonomer compounds of the present invention which exhibit a highsolubility in the solvents in which the polymerization will be carriedout and a reactivity comparable with that of the double bonds carried bythe monofunctional monomer and of those carried by the polyfunctionalmonomers which make possible the crosslinking, so as to obtain an evendistribution of the crosslinking nodes.

The membranes obtained from the compounds of the present invention canbe used in particular in dialysis systems, as separator in a two-phasereactor or for membrane processes of chlorine-sodium hydroxide type, orfor the recovery of effluents, or as electrolyte in a fuel cell. Asregards fuel cells, a macromolecular material obtained from monomercompounds of the invention can also be used as binder in the electrodematerial.

The monomer compounds of the present invention can be used for thecatalysis of various types of chemical reactions and in particular forpolymerization reactions, condensation reactions, addition orelimination reactions, oxidation or reduction reactions, solvolyses,Friedel-Crafts reactions and Diels-Alder reactions. For theseapplications in catalysis, the monomer compounds will be chosenessentially according to the cation associated with the anionic part.For the catalysis of Diels-Alder reactions or of Friedel—Craftsreactions, alkali metal, alkaline earth metal, transition metal or rareearth metal cations are preferred. It is also possible to use, for theabovementioned catalytic reactions, polymers obtained from theabovementioned monomer compounds. Polyanionic polymers comprising H⁺,Li⁺, Mg⁺⁺, Ca⁺⁺, Cu⁺⁺, Zn⁺⁺, Al⁺⁺⁺ or Fe⁺⁺⁺ cations or rare earth metalcations are preferred. Said polymers are generally put into the powderor granule form. In this case, the separation of the reactants becomesparticularly easy due to the insolubility of the polyanion of theinvention.

The compounds of the invention in which the cation is an onium of thediazonium, sulfonium, iodonium or metallocenium type can be used ascationic polymerization initiator. Under the action of actinicradiation, such compounds generate the corresponding acid form capableof initiating a cationic polymerization reaction. It is also possible touse polymers obtained by polymerization of the abovementioned monomercompounds. The advantages related to the use of polymers are analogousto those of the polymers used in the other abovementioned catalyticreactions. The materials of the invention in the amine salt form can beused as initiator of cationic polymerizations by heating, releasing thecorresponding protonic form. Likewise, if the cation is a salt of acationic azo compound (for example as represented below), it can act, byheating, as initiator of radical polymerizations.

The present invention is described in more detail by the followingexamples, the invention not being restricted to these examples.

EXAMPLE 1

An azeotropic distillation of 20 mmol of carboxylic acid ClCF₂CFClCOOHand of 10 mmol of hydrazine monohydrate was carried out in 200 ml oftoluene. After 24 hours, the toluene was evaporated and the compoundClCF₂CFClCONHNHCOCFClCF₂Cl was obtained. This compound was subsequentlydissolved in 200 ml of PCl₅ comprising 40 mmol of dimethylanilinehydrochloride. After having brought this mixture to reflux for 24 hours,two phases were obtained after cooling, including a denserClCF₂—CFCl—CCl═N—N═CCl—CFCl—CF₂Cl phase. This product was recoveredusing a separating funnel, washed with water and then treated withaqueous ammonia in a mixture of 100 ml of ether and 100 ml of a 4Maqueous ammonia solution. After stirring for 24 hours, the solvents wereevaporated and ClCF₂—CFCl—C(NH₂)═N—N═C(NH₂)CFClCF₂Cl was thus obtained.The latter product was subsequently brought to reflux in 100 ml ofbutanol for 48 hours and then, after the evaporation of butanol, takenup in 100 ml of anhydrous THF comprising zinc. After 24 hours, thesolvent was evaporated and the residual product recrystallized from asaturated KCl solution. After filtration, the recrystallized compoundwas ground up together with ammonium sulfate and then sublimed undervacuum, and the following compound was thus recovered:

EXAMPLE 2

10 mmol of hydrazine monohydrate were treated in THF with 15 mmol ofCF₃CO₂C₂H₅. After 8 hours, the THF was evaporated and the product dried.CF₃CONHNH₂ was obtained quantitatively. An azeotropic distillation ofthis compound with 10 mmol of the carboxylic acid ClCF₂CFClCOOH was thencarried out in 200 ml of toluene. After 24 hours, the toluene wasevaporated and ClCF₂CFClCONHNHCOCF₃ was obtained. This compound wassubsequently treated by a process analogous to that described in Example1 for the compound ClCF₂CFClCONHNHCOCFClCF₂Cl and the following compoundwas obtained:

EXAMPLE 3

10 mmol of trifluorovinyl iodide CF₂═CFI were slowly added to 30 ml ofanhydrous THF at 0° C. under argon comprising 20 mmol of zinc. Afterstirring for two hours, the excess zinc was removed by filtration underargon. 5 mmol of the lithium salt of 2,5-dibromo-1,3,4-triazole and 1mmol of Pd[P(C₆H₅)₃]₄ as catalyst were then added to the zincicsolution. After stirring for 24 hours, the solvent was evaporated andthen the residue was ground up together with ammonium hydrogensulfate.After subliming this mixture, the following compound was obtained:

EXAMPLE 4

10 mmol of the lithium salt of urazole and 500 μmol of1,8-bis(dimethylamino)anthracene were introduced into 50 ml of THF in achemical reactor. After having brought the reaction mixture to −20° C.,20 mmol of tetrafluoroethylene (PCR) were introduced slowly into thereactor. After 24 hours, the reaction mixture was flushed with argon andthen the mixture was allowed to slowly return to room temperature. 30mmol of sodium tert-butoxide, in solution in 20 ml of anhydrous THF,were then slowly added. After 3 hours, the solvent was evaporated andthe residue was recrystallized from a saturated KCl solution and thensublimed, after having been ground up together with ammonium sulfate.The following compound was obtained:

EXAMPLE 5

10 mmol of 1-trifluoromethyl-3-hydroxy-2,4,5-triazole were reacted with10 mmol of tetrafluoroethylene by a process similar to that described inExample 4. The following compound was thus obtained:

EXAMPLE 6

10 mmol of freshly sublimed malononitrile were dissolved in 50 ml ofanhydrous THF and then the solution was brought to 0° C. 20 mmol oflithium hydride LiH were then added portionwise. After 2 hours, 10 mmolof ClCF₂CFClSO₂F were added. After 48 hours, the solution wascentrifuged in order to remove the LiF precipitate and then the solventwas evaporated.

EXAMPLE 7

25.5 g of the acid chloride BrC₆H₄SO₂Cl were suspended in a solution of5.4 g of ammonium chloride in 100 ml of water maintained at 0° C. andthen 108 g of 15% sodium hydroxide solution were gradually added withvigorous stirring, the addition being controlled so that the pH did notexceed 10.5. The stoichiometric ratio of the reactants was 2:1:4. Thereaction scheme is:

2BrC₆H₄SO₂Cl+NH₄Cl+4NaOH→3NaCl+(BrC₆H₄SO₂)₂NNa+4H₂O.

The solution was subsequently filtered and then evaporated and thesodium salt of the bis(4-bromobenzenesulfonimide) (BrC₆H₄SO₂)₂NNa wasextracted with anhydrous ethanol. The salt was recrystallized from amethanol-methyl ethyl ketone mixture.

EXAMPLE 8

24.5 g of 1,1,1,2-tetrafluoroethane were condensed in 300 ml ofanhydrous ether at −78° C. 44 ml of a 10M solution of butyllithium inhexane were subsequently added dropwise with stirring. After one hour,250 ml of a commercial 1M solution of zinc chloride in ether were addedto the reaction mixture. The reaction was carried out according to thefollowing reaction scheme:

CF₃C₂H₂F+C₄H₉Li→C₄H₁₀+CF₂═CFLi+HF

CF₂═CFLi+ZnCl₂→CF₂═CFZnCl+LiCl

The suspension containing the zincic trifluorovinyl was brought back toordinary temperature and 45 g of the sodium salt ofbis(bromophenylsulfonimide) (prepared according to the procedure ofExample 7) in 150 ml of anhydrous dimethylformamide were added, as wellas 800 mg of trisbenzylideneacetonedipalladium(0) and 1 g oftriphenylphosphine. The ether was subsequently removed by distillationwhile flushing with dry argon and the mixture was maintained at 70° C.for six hours. The reaction product was filtered and the DMF was removedusing a rotary evaporator under partial vacuum at 60° C. The solidresidue was taken up in 100 ml of water and filtered. Thetetraethylammonium salt of the bis(trifluorovinylphenylsulfonimide) wasprecipitated by addition of 20 g of (C₂H₅)₄NCl in solution in 50 ml ofwater. The crude product was recrystallized from an ethanol-watermixture. It corresponds to the formula:

EXAMPLE 9

302 g of iodophenylsulfonyl chloride IC₆H₄SO₂Cl (commercial “pipsylchloride”) were dissolved in 1 l of acetonitrile at 25° C. and 105 g oftrifluoromethanesulfonaminde and 225 g of1,4-diazabicyclo-[2,2,2]-octane (DABCO) were added. The mixture wasstirred for 8 hours, during which a DABCO hydrochloride precipitate wasformed. The reaction mixture was subsequently filtered and the solventevaporated. The solid residue was taken up in 300 ml of a saturatedpotassium chloride solution and 100 ml of acetic acid. The precipitateformed, which corresponds to the formula:

was separated by filtration and recrystallized from water.

362.6 g of the salt thus prepared were dissolved in 700 ml of DMF and185 g of the zincic derivative in ether prepared by a process similar tothat described in Example 8, as well as 2.5 g oftrisbenzilidenedipalladium(0) and 4 g of triphenylphosphine, were added.The ether was subsequently distilled off under an argon flow and themixture was maintained at 60° C. with stirring for 5 hours. The reactionproduct was filtered and the DMF was removed using a rotary evaporatorunder partial vacuum at 60° C. The solid residue was washed with watersaturated with KCl, dried and then washed with dichloromethane. The saltobtained was purified by crystallization from a water-ethanol mixture.It corresponds to the formula:

EXAMPLE 10

40 g of the monofunctional ionic monomer prepared according to theprocedure described in Example 9 and 2.9 g of the difunctional ionicmonomer prepared according to the procedure of Example 8 were dissolvedin 100 ml of DMF. 7.5 g of colloidal silica [composed of particleshaving a mean size of 0.007 microns (Aldrich 38,126-8)] and 600 mg of1,2-diphenyl-1-keto-2,2-dimethoxyethane

were added to the solution thus obtained. The suspension was homogenizedand degassed by sparging with nitrogen, then sprayed as a 60 μm layerover a film of poly(ethylene terephthalate) (PET), and finally subjectedfor 50 seconds to UV irradiation of 1 W/cm² produced by a lamp ofHanovia type. The film was maintained under a nitrogen blanket duringthe exposure and the postcure of 5 minutes. The viscous solutionsolidified to form an elastic film. The DMF was removed by stoving for48 hours at 80° C., which made it possible to separate thepolyelectrolyte membrane from its PET support. The membrane was washedwith aqueous acidic solution (1M nitric acid solution) renewed severaltimes. The ions (K+TEA) of the membrane thus obtained were exchanged byprotons. The membrane was washed with distilled water and then driedunder vacuum to give a rigid film having a thickness of approximately 18μm and a very good mechanical strength.

EXAMPLE 11

4 g of the monofunctional ionic monomer prepared according to theprocedure described in Example 9 and 0.7 g of the difunctional ionicmonomer prepared according to the procedure of Example 8 were dissolvedin 15 ml of DMF and emulsified by vigorous mechanical stirring intoluene, using 500 mg of Brij 35® as surfactant. After degassing, thepolymerization was initiated at 80° C. with 100 mg of benzoyl peroxideand the polymerization was continued for 3 hours at this temperature.The crosslinked suspension of polymer was filtered and then washed withwater and with methanol, so as to remove the DMF. After drying, a fineresin powder was obtained. The cations associated with the sulfonimidegroups were exchanged for yttrium ions by stirring 2 g of the resinobtained in 6 successive baths of 10 ml of 1M yttrium chloride. Theresin was dehydrated. It has catalytic properties, in particular in theDiels-Alder and Friedel-Crafts reactions, in organic solvents. The useof the resin as catalyst is particularly advantageous because of itsinsolubility, which makes possible separation after the reaction bysimple filtration of the reaction mixture.

EXAMPLE 12

46.4 g of commercial 4-hydroxybenzenesulfonic acid sodium salt weredried under vacuum at 60° C. to remove the water of crystallization andthen dissolved in 150 ml of anhydrous ethanol, to which were added 14 gof sodium ethoxide and then 28 g of 2-methyl-2-bromopropane. Thesolution was filtered and the solvent evaporated to dryness. The sodium4-t-butoxybenzenesulfonate was recrystallized from a mixture of ethanoland ethyl acetate. 21.4 g of (chloromethylene)dimethylammonium chloride[CH(Cl)═N(CH3)₂]⁺Cl⁻ were added to 42 g of this salt in suspension in200 ml of anhydrous DMF, the mixture was stirred for 1 hour at 25° C.and then 5.8 g of lithium nitride were added. After reacting for 8hours, the mixture was filtered and the DMF was removed using a rotaryevaporator under partial vacuum at 60° C. The solid residue was taken upin 40 ml of trifluoroacetic acid, which catalyzes the solvolysisreaction of the t-butyl ether. The acid was subsequently distilled offand the mixture was taken up in 80 ml of water with 14 g of potassiumcarbonate. The residue, after evaporation of the water, was extracted inethanol and the following salt was obtained:

which was recrystallized from this solvent. 22 g of this salt weresuspended in 150 ml of THF in a Parr reactor with 1 g of potassiumt-butoxide. The reactor was purged under argon and tetrafluoroethylenewas introduced under a pressure of 5 bar. After one hour, the pressurefell to 1 atmosphere and the reactor was flushed with argon. The saltobtained, having the formula

was treated with 13.4 g of potassium t-butoxide in 50 ml of anhydrousTHF. The reaction product was filtered and then evaporated. The monomersalt obtained:

is recrystallized from water.

EXAMPLE 13

18.3 g of the compound

prepared according to the procedure described in Example 12, wassuspended in 100 ml of anhydrous DMF in a reactor with 2.6 g of sodiumhydride. After cessation of the evolution of hydrogen, 7 g of1,2-dibromotetrafluoroethane were added. The mixture was stirred at 60°C. for 2 hours. The reaction product was subsequently filtered, the DMFevaporated and the residue taken up in water and filtered. The crystalsof

were dewatered and dried.

This product was reduced in 150 ml of anhydrous acetonitrile at refluxunder argon with 8 g of zinc powder. The resulting solution wasfiltered, in order to remove the excess zinc, and then evaporated. Asalt identical to the preceding example was obtained and recrystallizedfrom an ethanol-water mixture.

This monomer easily polymerizes by heating, in particular inconcentrated solution, more conveniently in nonvolatile solvents, suchas propylene carbonate, to give, at 150° C., a thermostable linearpolymer:

In the presence of a monofunctional comonomer, this monomer behaves as adifunctional monomer, allowing crosslinking.

EXAMPLE 14

100 g of ClCF₂CFClSO₂F were synthesized according to the methoddescribed by Forohar Farhad (“Studies of the Chemistry ofPerfluorovinylsulfonyl Fluoride”, Clemson University, Thesis 1990 UMI9115049).

10 mmol of freshly sublimed malononitrile were dissolved in 50 ml ofanhydrous THF and then the solution was brought to 0° C. 20 mmol oflithium hydride LiH were then added portionwise. After 2 hours, 10 mmolof ClCF₂CFClSO₂F were added. After 48 hours, the solution wascentrifuged to remove the LiF precipitate and then 20 mmol of activatedzinc were added. After stirring for 24 hours, the THF was evaporated andthe residue taken up in acetonitrile and then filtered. Afterevaporation of the filtered solution and drying, the following compoundwas obtained:

EXAMPLE 15

10 mmol of trifluorovinyl iodide CF₂═CFI were slowly added to 30 ml ofanhydrous THF at 0° C. under argon comprising 20 mmol of zinc. Afterstirring for two hours, the excess zinc was removed by filtration underargon. 5 mmol of the potassium salt of bis(chlorosulfonyl)imide and 1mmol of Pd[P(C₆H₅)₃]₄, as catalyst, were then added to the zincicsolution. After stirring for 24 hours, the solvent was evaporated andthen the residue was recrystallized from a saturated potassium chloridesolution. After filtering and drying, the following compound wasrecovered:

The lithium salt was obtained by ionic exchange with lithium chloride intetrahydrofuran.

What is claimed is:
 1. A membrane comprised of a crosslinked copolymerof at least two ionic compounds in which the negative charge is highlydelocalized, corresponding to the formula [CF₂═CF—A⁻]_(m)M^(m+) inwhich: M^(m+) is a proton or a metal cation having the valency m chosenfrom the alkali metal, alkaline earth metal, transition metal or rareearth metal ions or an organic onium cation or an organometallic cation,1≦m≦3; A is an anionic group having one of the formulae (I)[—(CF₂)_(n)—SO₂Z]⁻, (II) [—(O)_(n′)—Φ—SO₂Z]⁻ or (III)

n and n′ represent 0 or 1; Φ represents a condensed or noncondensedaromatic group, which may or may not carry one or more substituents andwhich may or may not comprise heteroatoms, or a polyharlongenated group—C₆H_((4−x−y))F_(x)Cl_(y)— (1≦x+y≦4); Z represents —O or one of the—NC≡N, —C(C≡N)₂, —NSO₂R or —C[SO₂R]₂ groups, Z being other than —O whenn or n′ are zero; D represents a single bond, an oxygen atom, a sulfuratom, a —CO— carbonyl group or an —SO₂— sulfonyl group; the groups X¹ toX⁴, hereinafter denoted by X^(i), represent N, C—C≡N, CR, CCOR or CSO₂R,it being understood that, in a pentacyclic group, the x^(i) groups canbe identical or different; R represents Y, YO—, YS—, Y₂N—, F,R_(F)═C_(q)F_(2q+1) (preferably 0≦q≦12), CF₂═CF—, CF₂═CFCF₂— orCF₂═CF—O—, it being understood that, if 2 R substituents are present onthe same group, they can be identical or different; Y represents H or amonovalent organic radical having from 1 to 16 carbon atoms chosen fromalkyl, alkenyl, oxaalkyl, oxaalkenyl, azaalkyl, azaalkenyl, aryl oralkylaryl radicals or from the radicals obtained from the abovementionedradicals by substitution, in the chains and/or the aromatic part, byheteroatoms, such as halogens, oxygen, nitrogen, sulfur or phosphorus,it being understood that, if sulfur or phosphorus are present, they canoptionally be bonded to substituted nitrogen or oxygen atoms, or else Yis a repeat unit of a polymeric backbone; and at least one of the ioniccompounds carries only one CF₂═CF— group and at least one of the ioniccompounds carries at least two CF₂═CF— groups.
 2. A membrane accordingto claim 1, characterized in that M^(m+) is a metal cation chosen fromthe group consisting of Li⁺, K⁺, Mg⁺⁺, Ca⁺⁺, Ba⁺⁺, Cu⁺⁺, Zn⁺⁺, Fe⁺⁺ andRe⁺⁺⁺.
 3. A membrane according to claim 1, characterized in that M^(m+)is an ammonium [N(Y^(j))₄]⁺, an amidinium RC[N(Y^(j))₂]₂ ⁺, aguanidinium C[N(Y^(j))₂]₃ ⁺, pyridinium [C₅N(Y^(j))₆]⁺, an imidazoliumC₃N₂(Y^(j))₅ ⁴, an imidazolinium C₃N₂(Y^(j))₇ ⁺, a triazoliumC₂N₃(Y^(j))₄ ⁺, a carbonium C₅(Y^(j))₅C⁺, an NO⁺ (nitrosyl), NO₂ ⁺, asulfonium [S(Y^(j))₃]⁺, a phosphonium [P(Y^(j))₄]⁺ or an iodonium[I(Y^(j))₂]⁺, the Y^(j) substituents of the same cation, which can beidentical or different, representing one of the substituents indicatedfor Y.
 4. A membrane according to claim 1, characterized in that M^(m+)is an organometallic cation chosen from metalloceniums; metal cationscoordinated by atoms, such as O, S, Se, N, P or As, carried by organicmolecules, these cations optionally forming part of a polymericbackbone; or a trialkylsilyl, trialkylgermanyl or trialkylstannyl group.5. A membrane according to claim 1, characterized in that the M⁺ cationis the repeat unit of a conjugated polymer in cationic oxidized form. 6.A membrane according to claim 1, characterized in that the divalentradical Φ is a phenyl C₆H₄ corresponding to the ortho, meta and parapositions of substitution or an aromatic group, a phenyl which issubstituted and/or comprising condensed nuclei which may or may notcomprise heteroatoms.
 7. A membrane according to claim 1 wherein theionic compound which carries only one CF₂═CF— group is selected from thegroup consisting of ([CF₂═CF—SO₂NCN]⁻)_(m)M^(m+),([CF₂═CF—SO₂C(CN)₂]⁻)_(m)M^(m+), ([CF₂═CFCF₂—SO₂NCN)⁻)_(m)M^(m+),([CF₂═CFCF₂—SO₂C(CN)₂]⁻)_(m)M^(m+), ([CF₂═CF—ΦSO₂NCN]⁻]_(m)M^(m+),([CF₂═CF—ΦSO₂C(CN)₂]⁻)_(m)M^(m+), ([CF₂═CF—ΦSO₂NSO₂CF₃]⁻)_(m)M^(m+),([CF₂═CF—ΦSO₂C(SO₂CF₃)₂]⁻)_(m)M^(m+),([CF₂═CF—ΦSO₂CH(SO₂CF₃)]⁻)_(m)M^(m+),


8. A membrane according to claim 1 wherein the ionic compound whichcarries at least two CF₂═CF— groups is selected from the groupconsisting of ([CF₂═CF—SO₂)₂)₂N]⁻)_(m)M^(m+),([CF₂═CFCF₂—SO₂)₂N]⁻)_(m)M^(m+), ([(CF₂═CFSO₂)₂CH]⁻)_(m)M^(m4),([(CF₂═CFCF₂—SO₂)₂CH]⁻)_(m)M^(m+), ([(CF₂═CF—SO₂)₃C]⁻)_(m)M^(m+),([(CF₂═CFCF₂—SO₂)₃C]⁻)_(m)M^(m+), ([(CF₂═CF—ΦSO₂)₂N]—)_(m)M^(m+),([(CF₂═CF—O—ΦSO₂)₂N])_(m)M^(m+), ([(CF₂═CF—ΦSO₂)₂CH]⁻)_(m)M^(m+),([(CF₂═CF—O—ΦSO₂)₂CH]⁻)_(m)M^(m+), ([(CF₂═CF—ΦSO₂)₃C]⁻)_(m)M^(m+),([(CF₂═CF—O—ΦSO₂)₂CH]⁻)_(m)M^(m+), ([(CF₂═CF—ΦSO₂)₃C]⁻)_(m)M^(m+),([(CF₂═CFΦSO₂)₂CH]⁻)_(m)M^(m+), ([(CF₂═CF—O—ΦSO₂)₂CH]⁻)_(m)M^(m+),([(CF₂═CF—ΦSO₂)₃C]⁻)_(m)M^(m+), ([(CF₂═CF—O—ΦSO₂)₂CH]⁻)_(m)M^(m+),([(CF₂═CF—ΦSO₂)₃C]⁻)_(m)M^(m+), ([(CF₂═CF—O—ΦSO₂)₃C]⁻)_(m)M^(m+),([(CF₂═CF—)₂C₆H₃SO₃]⁻)_(m)M^(m+),([3,5-(CF₂═CF—)₂C₆H₃SO₂NSO₂CF₃]⁻)M^(m+)


9. A membrane comprised of a crosslinked copolymer of at least two ioniccompounds in which the negative charge is highly delocalized,corresponding to the formula [CF₂═CF—A⁻]_(m)M^(m+) in which: M^(m+) is aproton or a metal cation having the valency m chosen from the alkalimetal, alkaline earth metal, transition metal or rare earth metal ionsor an organic onium cation or an organometallic cation, 1≦m≦3; A is ananionic group having one of the formulae (I) [—(CF₂)_(n)—SO₂Z]⁻, (II)[—(O)_(n′)—Φ—SO₂Z]⁻ or (III)

n and n′ represent 0 or 1; Φ represents a condensed or noncondensedaromatic group, which may or may not carry one or more substituents andwhich may or may not comprise heteroatoms, or a polyharlongenated group—C₆H_((4−x−y))F_(x)Cl_(y)— (1≦x+y≦4); Z represents —O or one of the—NC≡N, —C(C≡N)₂, —NSO₂R or —C[SO₂R]₂ groups, Z being other than —O whenn or n′ are zero; D represents a single bond, an oxygen atom, a sulfuratom, a —CO— carbonyl group or an —SO₂— sulfonyl group; the groups X¹ toX^(4,), hereinafter denoted by X^(i), represent N, C—C≡N, CR, CCOR orCSO₂R, it being understood that, in a pentacyclic group, the x^(i)groups can be identical or different; R represents Y, YO—, YS—, Y₂N—, F,R_(F)═C_(q)F_(2q+1) (preferably 0≦q≦12), CF₂═CF—, CF₂═CFCF₂— orCF₂═CF—O—, it being understood that, if 2 R substituents are present onthe same group, they can be identical or different; Y represents H or amonovalent organic radical having from 1 to 16 carbon atoms chosen fromalkyl, alkenyl, oxaalkyl, oxaalkenyl, azaalkyl, azaalkenyl, aryl oralkylaryl radicals or from the radicals obtained from the abovementionedradicals by substitution, in the chains and/or the aromatic part, byheteroatoms, such as halogens, oxygen, nitrogen, sulfur or phosphorus,it being understood that, if sulfur or phosphorus are present, they canoptionally be bonded to substituted nitrogen or oxygen atoms, or else Yis a repeat unit of a polymeric backbone; and at least one of the saidat least two ionic compounds has all R substituents selected from Y,YO—, YS—, Y₂N—, F, or C_(q)F_(2q+1), and at least one of the said atleast two ionic compounds has at least one substituent R selected fromCF₂═CF—, CF₂═CFCF₂— or CF₂═CF—O—.
 10. A method for preparing a membrane,comprising the step of copolymerizing at least two ionic compounds inwhich the negative charge is highly delocalized, corresponding to theformula [CF₂═CF—A⁻]_(m)M^(m+) in which: M^(m+) is a proton or a metalcation having the valency m chosen from the alkali metal, alkaline earthmetal, transition metal or rare earth metal ions or an organic oniumcation or an organometallic cation, 1≦m≦3; A is an anionic group havingone of the formulae (I) [—(CF₂)_(n)—SO₂Z]⁻, (II) [—(O)_(n′)—Φ—SO₂Z]⁻ or(III)

n and n′ represent 0 or 1; Φ represents a condensed or noncondensedaromatic group, which may or may not carry one or more substituents andwhich may or may not comprise heteroatoms, or a polyhalogenated group—C₆H_((4−x−y))F_(x)Cl_(y)— (1≦x+y≦4); Z represents —O or one of the—NC≡N, —C(C≡N)₂, —NSO₂R or —C[SO₂R]₂ groups, Z being other than —O whenn or n′ are zero; D represents a single bond, an oxygen atom, a sulfuratom, a —CO— carbonyl group or an —SO₂— sulfonyl group; the groups X¹ toX⁴, hereinafter denoted by X^(i), represent N, C—C≡N, CR, CCOR or CSO₂R,it being understood that, in a pentacyclic group, the X^(i) groups canbe identical or different; R represents Y, YO—, YS—, Y₂N—, F,R_(F)═C_(q)F_(2q+1) (preferably 0≦q≦12), CF₂═CF—, CF₂═CFCF₂— orCF₂═CF—O—, it being understood that, if 2 R substituents are present onthe same group, they can be identical or different; Y represents H or amonovalent organic radical having from 1 to 16 carbon atoms chosen fromalkyl, alkenyl, oxaalkyl, oxaalkenyl, azaalkyl, azaalkenyl, aryl oralkylaryl radicals or from the radicals obtained from the abovementionedradicals by substitution, in the chains and/or the aromatic part, byheteroatoms, such as halogens, oxygen, nitrogen, sulfur or phosphorus,it being understood that, if sulfur or phosphorus are present, they canoptionally be bonded to substituted nitrogen or oxygen atoms, or else Yis a repeat unit of a polymeric backbone; at least one of the ioniccompounds carries only one CF₂═CF— group and at least one of the ioniccompounds carries at least two CF₂═CF— groups, and forming a membranewith the copolymer.
 11. The method according to claim 10, wherein M^(m+)is a metal cation chosen from the group consisting of Li⁺, K⁺, Mg⁺⁺,Ca⁺⁺, Ba⁺⁺, Cu⁺⁺, Zn⁺⁺, Fe⁺⁺ and Re⁺⁺⁺.